CATIONIC LIPOSOMES IMPROVE STABILITY AND INTRACELLULAR DELIVERY OF ANTISENSE OLIGONUCLEOTIDES INTO CASKI CELLS

Antisense oligonucleotides (ODNs) are promising novel therapeutic agen ts against viral infections and cancer. However, problems with their i nefficient delivery and inadequate stability have to be solved before they can be used in therapy. To circumvent these obstacles, a wide var iety of improvements, including phosphorothioate ODNs and liposomes as a carrier system, have been developed. This study was designed to com pare the effects of two cationic liposomes on the intracellular delive ry and stability of ODNs in CaSki cell cultures. Also the stability of 3'-end phosphorothioate ODNs were investigated. The 3'-modification n either had any effect on the delivery, nor protected the ODNs against degradation. The cellular delivery and stability of ODNs was improved with both cationic liposomes, but a cationic liposomal preparations co ntaining dimethyldioctadecylammonium bromide and dioleoylphosphatidyle thanolamine (DDAB/DOPE) was more efficient than commercially available N-(1-(2,3-dioleoyIoxy)propyl)-N, N, N-trimethylammoniummethylsulfate (DOTAP). The improved cellular delivery was largely due to the stabili zation of ODNs by cationic liposomes. The improved stability in the cu lture medium indicates that the cationic liposomes per se protect the ODNs from enzymatic degradation. Indeed, intact ODNs were found in the cytoplasm and nucleus only when delivered by cationic liposomes.